1. Field of the Invention
This invention relates to a technique associated with an ice blasting process, more particularly, an apparatus for producing and ejecting ice pellets, and a method of using ice blasting to perform the finishing process on film-insert injection moldings.
2. Description of the Related Art
Ice blasting apparatus using slurry that includes a mixture of ice pellets and water as an emitted material does not use any abrasive, and therefore does not cause any damage to articles undergoing the blasting process. Further, the ice blasting apparatus has no abrasive residues left after the completion of the blasting process and thus is in no need of a disposal process for liquid wastes that includes an abrasive. For these reasons, such ice blasting apparatuses have captured much of the spotlight as next-generation blasting apparatuses, and are being assiduously developed for eventual commercialization.
Ice blasting is an epoch-making technique having various advantages. Because of a great problem involved in commercialization, ice blasting falls short of completely replacing conventional dry blasting and wet blasting using abrasives. More specifically, ice blasting uses ice pellets instead of abrasives. Hence, although it goes without saying that definitive methods for producing and supplying ice pellets are of significant importance, there is a considerably difficult problem in implementing the stable producing and supplying of the ice pellets at low cost from a practical point of view, aside from the theory. In other words, unlike usual abrasives, ice pellets have the unstable property of being incapable of keeping their form at room temperature, making stocking unfeasible. Therefore, ice pellets must be continuously supplied to a blast gun while being produced. A high technique is necessary to continue to stably and continuously produce and supply ice pellets of the form best suited for the emitted material, which in turn requires high costs.
In order to finish a surface of a molding with a required accuracy by the use of ice blasting, the concentrations of ice slurry blasted from a blast gun need to be set precisely. If the concentrations are not properly controlled, there is not even the remotest possibility of yielding satisfactory result of the blasting process. In other words, because the ice blasting apparatus uses as a material melting-prone and unstable ice, there is a need of concentration control with a far higher degree of precision than that in conventional blasting apparatuses that use a material of significantly stable properties as an abrasive.
As described above, a requirement for implementing the effective ice blasting process is combined operation between an ice making device capable of stably producing and supplying ice pellets with high accuracy and an ice mixing tank capable of stably producing and supplying ice slurry of a properly controlled concentration in accordance with the ice pellets supplied thereto. Up to now, however, it has been virtually impossible to find an ice blasting apparatus using such an ice making device and an ice mixing tank, which has been perfected so as to be capable of giving a high degree of satisfaction from all aspects.
When it comes to the film insert molding, this is composed of a resin molding and a film material integrally adhering to the surface of the resin molding. To manufacture the film insert molding, a film material made of acrylic resin or the like is laid inside a cavity of an injection mold. Then, the injection mold is closed and molten resin such as polypropylene or the like is injected into the cavity of the injection mold. The resulting film insert molding is adopted widely for interior vehicle components such as a console, a center cluster and a switch base, parts of various household electric appliances (e.g. the display panel of a refrigerator, a washing machine or the like), various furnishings, and various building materials such as wallboards and pillars.
As illustrated in the perspective view of FIG. 2 and the sectional view of FIG. 3 which is taken along the A—A line in FIG. 2, in the film insert molding immediately after being removed from the injection mold, a film material 32 is adhering to a resin molding 31 with extending beyond the outer periphery edge and the inner periphery edge of the resin molding 31. For final completion of the film insert molding, a process is required for trimming the unnecessary extending portion 39.
This process is typically performed by manual work in which an operator cuts off the extending portion 39 gently by use of a box cutter. The resin molding often has a complicated peripheral shape. Further, the film material 32 is soft and unsteady. Hence, paying close attention is required for the cutting process using a box cutter. Time and effort are naturally required, which in turn makes bulk handling in a short time impossible. Further, the resin molding 31 and/or the film material 32 integrally adhering to the surface of the resin molding 31 may be damaged during the cutting process. Many defective products are produced, making shipment impossible.
Under the circumstances, in one case an attempt is made to immerse the resin molding 31 with the unnecessary extending portion 39 in liquid nitrogen in order for the extending portion 39 to be chilled to an extreme low temperature to freeze and weaken, and then for the frozen extending portion 39 to be crushed for removal. However, this attempt has not yet been successfully put into actual use because of the high cost required for facilities and the overstressing of the resin molding 31.
In another case, an attempt is made to crush the extending portion 39 for removal by the use of a process of directing a dry blast of an abrasive toward the resin molding 31 by high pressure gas or a process of directing a wet blast of slurry having an abrasive suspended in fluid toward the resin molding 31. This attempt has met with some success. However, an abrasive is used as the emitted material in the dry blasting and the wet blasting. Hence, it is inevitable that the surface of the film material 32 is damaged and roughened to varying degrees when the abrasive comes into collision with the surface of the film material 32.
Some of various products in fact have a wide allowable range of a somewhat roughened surface of the film material 32. However, in the case of relatively high quality products such as an interior vehicle component composed of the resin molding 31 and a woodgrain-pattern printed film or a very smooth, glossy film adhering integrally to the surface of the resin molding 31, a roughened surface of the film material is undesirable. In view of this, there is hesitation over using the dry blasting and the wet blasting processes. As described hitherto, a blasting process is not able to be used as the finishing process for various resin moldings, particularly, a film insert molding, resulting in hindrance to any improvement in working efficiency.